Nitric Oxide Treatment Improves the Antioxidant Capacity While Inhibiting Anthocyanin Biosynthesis of Peach Fruit (‘Xiahui-8’) During Ripening

Nitric Oxide (NO) is an important bioactive signal molecule that plays an important role in diverse physiological processes. This study aimed to explore the effects of Nitric Oxide (NO) treatments on postharvest peach fruit. Specifically, we examined changes in quality attributes, antioxidant ability, and anthocyanin profiles during storage, given the important role of NO as a bioactive signal molecule in physiological processes. The peaches (cv. Xiahui-8) were subjected to a 3-hour fumigation with 10 μL L⁻¹ Nitric Oxide (NO) gas, followed by storage at room temperature (25 ± 2 °C) for 8 days. This treatment enhanced the fruit’s antioxidant capacity by suppressing free radical (H₂O₂, O₂^.-) and MDA generation and activating the activities of antioxidant enzymes (SOD, CAT) as well as their gene expression. Conversely, this treatment reduced red coloration intensity of peaches by repressing anthocyanin synthesis and the increase in colorimeter a* value. The content of pelargonidin 3-O-rutinoside appears to play a critical role in red pigment formation in peach fruit. This observation is supported by LC/MS and qPCR analyses, which revealed that anthocyanin levels and the transcript abundance of their structural genes were concomitantly reduced in NO-treated fruit. These findings collectively reveal a novel regulatory mechanism through which NO application influences anthocyanin synthesis in peach.